The present invention concerns compatible mixtures of relatively high molecular weight aminated polyether polyols and ethylene glycol containing a substituted urea.
Polyurethane articles, commonly formed by the Reaction Injection Molding (RIM) process, are polymer products resulting from the reaction of liquid polyol mixtures of high molecular weight polyether polyols (m.w. &gt;2000) and chain extenders such as ethylene glycol (EG) or 1,4 butane diol with liquid polyisocyanates. Other RIM processes utilize a blend of aliphatic and/or aromatic amine chain extenders (in the presence or absence of glycol chain extenders) and high molecular weight polyether polyols reacted with liquid polyisocyanates. Still other RIM processes are based on the blend of glycols such as ethylene glycol and amine terminated high molecular weight liquid polyethers to react with liquid polyisocyanates. This last named RIM process based on the use of amine terminated high molecular weight polyethers and ethylene glycol blends exhibit the following advantageous characteristics compared to systems utilizing ethylene oxide capped high molecular weight polyether polyols:
(A) Shows overall better processability with less skin delamination problems with the demolded RIM part and the RIM part exhibits a higher green strength at demold.
(B) RIM parts exhibiting fewer defects can be demolded at lower tool (mold) temperature. With less critical tool temperatures being required, the RIM part manufacturing results in advantageously wider processing "latitudes".
(C) Use of amine terminated high molecular weight polyethers and ethylene glycol blend as the reactive components yield RIM polymers that exhibit the following improvements in physical properties: a higher flexural modulus at the same ethylene glycol level compared to the use of high molecular weight polyether polyols; higher elongation values at tensile break at the same ethylene glycol level; and higher tear strengths (Die "C") at the same ethylene glycol levels.
The aforementioned improvements become more pertinent at the lower flexural modulus levels (lower ethylene glycol levels) of the RIM polymers or those polymers exhibiting low hardness values (&lt;95 shore A).
Although amine terminated high molecular weight polyethers plus ethylene glycol exhibit the above advantages, formulations based on this blend are incompatible fluids that tend to separate into layers on standing.
Recognition of this effect dictates that these blends should be constantly agitated to avoid a misformulation by the separation of components. If the blend of amine terminated polyether and glycol also contain a organometal catalyst, (such as an organotin compound) a catalyst separation may also occur.
We have discovered that the addition of a minor amount of a substituted urea to the incompatible blend of ethylene glycol and amine terminated high molecular weight liquid polyethers renders these mixtures into a compatible or single phase liquid. We have further discovered that the presence of these substituted ureas not only can compatibilize the above mentioned blends but also can serve as the sole catalyst for the reaction of amine/polyol blends with polyisocyanates. This is particularly advantageous since the commonly used organotin catalysts have been found to lose catalytic activity in the presence of amines over a period of time and the rate of catalyst (organotin) decay increases with an increase in storage temperature.